1. Field of the Invention
This invention relates to the field of tape guides for a magnetic tape drive system.
2. Background of the Problem
Tape drive systems for reading information from or writing information on magnetic tapes require tape guides to ensure that the tape is positioned correctly relative to the magnetic tape head. The tape must be driven past the tape head(s) in precise position so that the appropriate tracks of the tape are positioned relative to the heads.
One type of prior tape guide uses rollers having integral non-compliant fixed upper and lower flanges to guide the tape. Problems arising from this type of tape guide include friction generated from the tape movement against the fixed flanges which results in tape speed variations, tape resonance excitation, and tape debris generation. Also, the tape frequently varies in width, so that the flanges must be separated in excess of the tape width which results in vertical tape movement. The vertical displacement of the tape causes poor tracking of the tape as well as buckling and creasing of the tape as the tape encounters the roller.
Another type of prior tape guide uses cylindrically shaped air bearings having fixed, nonrotating lower flanges and fixed upper compliant members. The upper compliant members force the tape against the lower flange and the air bearings provide support to guide the tape into position. However, as the diameter of the tape being unwound or wound on the reels changes as the tape is wound or unwound, the "wrap angle", that is the angle formed between the tape and the tape guide, varies. The wrap angle variations result in exposure of the air bearing supply holes which cause an imbalance to the pneumatic system creating tape oscillations due to the impingement of the air. The air bearings also add considerably to the cost and mass of the drive as well as requiring an air supply to generate the air pressure for the bearings.
A need therefore exists for a tape guide which will guide the tape without regard to the wrap angle variations, which will provide a uniform distributed load on the tape to prevent vertical displacement of the tape and will reduce the mass and expense of the tape drive system.